Fig. 1

VNS electrode implantation and intraoperative verification of target engagement. A Surgical field following identification and careful dissection of the carotid sheath exposing the common carotid artery (CCA), internal jugular vein (IJV) and vagus nerve (VN). B Implantation of bipolar stimulation electrode on the vagus nerve with the cathode placed caudally to the anode. Notice the sternocleidomastoid (SCM) crossing the surgical field. C Representative time series of the response of heart rate (red) and respiration rate to VNS. Periods of VNS are represented by gray bars. D Intraoperative VNS was used to verify proper engagement between the VN and stimulating electrode. Average evoked responses for NHPs An, Dk, Rh1 and Rh2 demonstrate that 30 s of VNS (gray bars) evokes a robust, sustained parasympathetic response manifest as a greater than 20% reduction in the rate of respiration (black traces), with no apparent change in heart rate (red traces)